#!/bin/sh
# make-backup-file-name -- print the next numbered emacs-style backup file
#                          name for a given file on disk
# Author: Noah Friedman <friedman@prep.ai.mit.edu>
# Created: 1994-01-14
# Last modified: 1994-03-09
# Public domain

# Comments:

# Usage: make-backup-file-name [filename]
#
# Return the next emacs-style backup file name for a given file on disk,
# based on the VERSION_CONTROL environment variable.
# `t' or `numbered' means make numeric backup versions unconditionally.
# `nil' or `existing' means make them for files that have some already.
# `never' or `simple' means do not make them.

# Code:

name=$1
case "$VERSION_CONTROL" in
   never | simple ) result=$name~ ;;
   * )
     set `for f in "$name".~*~ ; do 
             echo "$f"
          done \
           | sed -ne 's/~$//
                      s/.*\.~//
                      p' \
           | sort -nr` > /dev/null
     highest=$1
     case "$highest" in
        '*' | '' ) highest=0 ;;
     esac
     case "$VERSION_CONTROL" in
        nil | existing )
           case "$highest" in
             0 ) result=$name~ ;;
           esac
        ;;
        t | numbered | * )
           next=`expr $highest + 1`
           result=$name.~$next~
        ;;
     esac
   ;;
esac
echo "$result"

# make-backup-file-name ends here